Source: BBC Radio 4: Today Programme
URL: N/A
Date: 05/06/2015
Event: Keith Shine on global warming: "sometimes it's faster and sometimes it's slower"
Credit: BBC Radio 4
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Justin Webb: Has there or has there not been a slowdown, a hiatus in global warming, over the last decade or so? The feeling has been that there has been a slowdown. People who claim that man-made warming is less important than it's jumped up to be have used the hiatus to back up their claim - after all, there's more carbon being pumped into the air but apparently with little immediate effect. Well, hold on. The National Oceanographic and Atmospheric Administration in the United States has reported that an apparent slowdown in the pace of global warming in recent years might, they say, be an illusion based on skewed data. The report raises questions about the way scientists calculate global warming, and indeed the interpretation of the data that they then come up with. Tom Karl is lead author of the report on climate change.
Tom Karl: What we recognised was that the observing system had changed, over the course of the last 10 to 20 years, in rather important ways that we needed to address. And then we had some new data sets introduced that had more data but also, more importantly, had information about how the data was collected. So clearly, when we have measurements we want to make best use of them, particularly if they're in areas where there's a dearth of observations.
Justin Webb: Let's turn to Keith Shine, who's Regius Professor of Meteorology and Climate Science at Reading University and is on the line from there - good morning.
Keith Shine: Good morning, Justin.
Justin Webb: What do you make of this?
Keith Shine: Well, it's a very important study - it's part of the natural progress of any science, that, um, you make advances in how to understand how we observe the climate system. So certainly, the - their analysis shows that the hiatus is not as much as we first thought. Er -
Justin Webb: But can we trust their analysis? I mean, what you said there at the beginning, you said the observing systems had changed, so the actual - they now think, do they, that the way that the temperature was measured, over this last crucial 10 to 15 years, has been faulty?
Keith Shine: Well, I wouldn't say "faulty" - it's, as I say, it's more that our understanding advances, I mean, you could say "faulty" about any scientific advance. But I mean, there's been a change in the way we analyse observations of sea-surface temperatures from ships, there are now different ways we observe, um, sea-surface temperature using floating buoys and also satellites. So it's these natural advances in science.
Justin Webb: So is it that we were measuring it too hot, at the turn of the century, and we've now, kind of, calibrated properly? Is that what we're talking about?
Keith Shine: Um, it - it's more that the rate of warming over the past 15 years is faster than we thought. Um... But, I mean, one thing that it's important to stress is that there's no absolute definition of "hiatus", and they've used one particular definition of "hiatus", which is looking at the - comparing the last 10 years with the previous, um, 50 years, but there is still something to explain in the warming in the last 15 years of last century was certainly warmer than the um, first 15 years of this century. So on that definition, um, there is still something to explain -
Justin Webb: I mean, you will know better than anyone that all the politics that surrounds this and the claims and counter-claims, and what people are going to say, who are sceptical about man-made global warming, is that this is too convenient, that this is an alteration of a story that had been told by everyone, including the UN body, the IPCC, who'd said that there had been some kind of a hiatus, and now suddenly the story's changed.
Keith Shine: Well, we must be very clear that the main picture about climate change hasn't - hasn't varied, actually, but even with this new analysis, the temperature change since the 1950s has been about 0.6 of a degree Centigrade, and the Intergovernmental Panel on Climate Change concluded it's extremely likely that this is predominantly due to human activity. So that big picture hasn't changed. What has - what has been an issue is that the warming that we've seen isn't steady, and we wouldn't expect it to be steady, it's slightly warmer in - slightly faster in some periods and slightly slower in others. And this past 15 years, it has been slightly slower than in some other periods. So, it's - one of the cutting edges of climate science is to explain why we get these departures from the average warming, that sometimes it's faster and sometimes it's slower.
Justin Webb: Keith Shine from Reading University, thanks.